Differences from the book

Not using Forge, FAKE or Paket

I decided not to use any of the following:

• Forge
• FAKE
• Paket

Actually, I did initially use FAKE and Paket but got rid of them after getting all the code working.

I added the following to src/FsTweet.Web/FsTweet.Web.fsproj to copy the assets and views directories:

  <Target Name="CopyCustomContentAfterBuild" AfterTargets="AfterBuild">
    <Exec Command="cp -r assets views $(OutDir)" />
  </Target>
  <Target Name="CopyCustomContentAfterPublish" AfterTargets="Publish">
    <Exec Command="cp -r assets views $(PublishDir)" />
  </Target>

Not using SQLProvider

I am using Entity Framework Core instead of SQLProvider because I could not get SQLProvider to work on .NET Core on macOS.

Not deploying to Azure

I decided to deploy to Heroku instead of Azure because I have more experience with Heroku. I am deploying with Docker.

Building

dotnet clean src/FsTweet.Web/FsTweet.Web.fsproj
dotnet build src/FsTweet.Web/FsTweet.Web.fsproj

Running locally

docker run --name postgres -e POSTGRES_USER=postgres -e POSTGRES_PASSWORD=test -p5432:5432 -d postgres:10.4-alpine
export DATABASE_URL=postgres://postgres:test@localhost:5432/FsTweet
export FSTWEET_ENVIRONMENT=dev
export FSTWEET_SUAVE_SERVER_KEY=<Suave server key>
export FSTWEET_SENDER_EMAIL_ADDRESS=<email address>
export FSTWEET_SITE_BASE_URL=https://fstweet-jt.herokuapp.com
export FSTWEET_POSTMARK_SERVER_KEY=<Postmark server key>
export FSTWEET_POSTMARK_TEMPLATE_ID=<Postmark template id>
export FSTWEET_STREAM_API_KEY=<Stream api key>
export FSTWEET_STREAM_API_SECRET=<Stream api secret>
export FSTWEET_STREAM_APPID=<Stream app id>
dotnet run --project src/FsTweet.Web/FsTweet.Web.fsproj

I use DATABASE_URL instead of FSTWEET_DB_CONN_STRING because I deploy to Heroku and use the Heroku Postgres add-on. As part of provisioning this add-on, Heroku adds the DATABASE_URL config var which has the following format:

postgres://{user}:{password}@{hostname}:{port}/{database-name}

Deploying

./deploy.sh

Migrating the database

Locally

export DATABASE_URL=postgres://postgres:test@localhost:5432/FsTweet
./migrate.sh

On Heroku

export DATABASE_URL=postgres://{user}:{password}@{hostname}:{port}/{database-name}
./migrate.sh -ssl

The -ssl flag adds the following extra connection string parameters:

SSL Mode=Require;Trust Server Certificate=true;

TODO

• CI/CD via CircleCI 2.0
• Add an additional variable to the Postmark email template for the base part of the URL
• Add version information and surface it in the Web UI somewhere (e.g. in the page title)
• Do some of the suggested excercises
  • Chapter 11
    • Send a welcome email on successful email verification
  • Chapter 15
    • Store user informarion in a database instead of a cookie
    • Use sliding expiration for the session cookie
  • Chapter 19
    • Send an email notification to followee when followee is followed by follower
    • Add support for unfollowing
• Add unit tests
• Add integration tests

Problems

DotLiquid extends

I encountered a problem with extends:

{% extends master_page.liquid %}

What was rendered in the browser was just the following error message:

Liquid error: Value cannot be null. Parameter name: path2

After some digging/experimentation, I got it working by doing this:

{% extends 'master_page.liquid' %}

Package woes

When I got rid of Paket, I re-added all the relevant packages via dotnet add e.g.

dotnet add src/FsTweet.Web/FsTweet.Web.fsproj package Suave

The project built and launched successfully. However, when sending a tweet, I encountered the following exception:

System.MissingMethodException: Method not found: 'System.Tuple`2<Microsoft.FSharp.Core.FSharpFunc`2<System.__Canon,Microsoft.FSharp.Core.FSharpOption`1<!!1>>,Microsoft.FSharp.Core.FSharpFunc`2<!!1,Microsoft.FSharp.Core.FSharpFunc`2<System.__Canon,System.__Canon>>> Prism.ofEpimorphism(Microsoft.FSharp.Core.FSharpFunc`2<System.__Canon,Microsoft.FSharp.Core.FSharpOption`1<!!1>>, Microsoft.FSharp.Core.FSharpFunc`2<!!1,System.__Canon>)'.
   at Chiron.Mapping.Json.writeWith[a](FSharpFunc`2 toJson, String key, a value)
   at Social.Suave.ToJson@158-6.Invoke(Unit unitVar) in /Users/jontaylor/HomeProjects/fsharp/tmp/FsTweet/src/FsTweet.Web/Social.fs:line 158
   at Chiron.Builder.Delay@193.Invoke(Json json)
   at Social.Suave.onFindFolloweesSuccess(FSharpList`1 users) in /Users/jontaylor/HomeProjects/fsharp/tmp/FsTweet/src/FsTweet.Web/Social.fs:line 207
   at Chessie.ErrorHandling.AsyncExtensions.Async.map@241.Invoke(a x)
   at Microsoft.FSharp.Control.AsyncBuilderImpl.args@506-1.Invoke(a a)

I ran dotnet publish for both the Paket based and non Paket based versions of the code and then compared the md5 hashes of all the dlls. Most of them were identical. The first one that differed was Aether.dll (brought in by Chiron ?). A bit of digging revealed that the Paket based version was using 8.2 of this dll whereas the non Paket based version was using 8.0.2. I explicitly added version 8.2:

dotnet add src/FsTweet.Web/FsTweet.Web.fsproj package Aether -v 8.2

After doing this and rebuilding, the problem went away.

Links

• F# Applied II